Method for processing colemanite ore

ABSTRACT

In the method, a hot gas is flowed linearly through a slightly inclined treating area. Colemanite ore particles are repeatedly elevated and dropped substantially vertically through the gas while they are simultaneously advanced countercurrent to the gas flow. This movement is continued until the ore particles are heated to the point of decrepitation at which they relatively suddenly break into a large number of relatively fine particles of substantially sure colemanite which are carried out of the treating area by the gas stream. The gas carried colemanite particles are then separated from the gas stream to provide an upgraded and classified product. Gas velocity and temperature and the path and rate of movement of the ore through the gas are varied as required to obtain a given grade or size in the recovered colemanite product. The apparatus used in practicing the method includes, in a preferred form, a tubular calcining drum which is inclined slightly with respect to the horizontal. Lifters are positioned along the internal wall of the calcining drum and the drum is rotated between two stationary end assemblies. Ore particles are introduced into the upper end of the drum and a stream of hot gas is introduced through the lower end of the drum. Rotation of the drum causes the ore to be repeatedly lifted and dropped across the gas stream while the ore simultaneously advances from the upper toward the lower end of the drum. The temperature of the advancing ore increases to the point required to cause decrepitation of the ore, and the gas stream flowing through the drum carries the particles of decrepitation to the upper end of the drum where they are removed and separated from the gas stream. In the preferred form, gas leaving the drum is conveyed to a second rotating, inclined drum which functions as a preheater for ore being introduced into the calcining drum.

United States Patent 1 Wilson et al.

[ METHOD FOR PROCESSING COLEMANITE ORE [75] Inventors: David Wilson, Houston, Tex.; Blair T. Burwell, Denver, C010.

[73] Assignee: Tenneco Oil Company, Houston,

Tex.

22 Filed: on. 23, 1973 21 Appl. No.: 408,318

Related US. Application Data [63] Continuation of Ser. No. 183,846, Sept. 27, 1971,

abandoned.

[52] US. Cl 432/13, 241/23, 432/103, 432/106 [51] Int. Cl. F27b 7/14 [58] Field of Search 241/17, 18, 19, 23, 24, 241/26, 47,54, 65, 68; 432/13, 103,106, 111

[56] References Cited UNITED STATES PATENTS 987,850 3/1911 Braddock 241/26 X 1,934,930 l1/l933 Kent 241/54 2,469,562 5/1949 Kennedy 432/13 2,526,355 10/1950 Hesse 241/54 3,202,502 8/1965 Lean et al.... 241/23 X 3,712,598 4/1971 Miles 263/32 R Primary Examiner-John J. Camby Attorney, Agent, or FirmTorres & Berryhill [5 7] ABSTRACT In the method, a hot gas is flowed linearly through a slightly inclined treating area. Colemanite ore parti- 51 Feb. 11, 1975 cles are repeatedly elevated and dropped substantially vertically through the gas while they are simultaneously advanced countercurrent to the gas flow. This movement is continued until the ore particles are heated to the point of decrepitation at which they relatively suddenly break into a large number of relatively fine particles of substantially sure colemanite which are carried out of the treating area by the gas stream. The gas carried colemanite particles are then separated from the gas stream to provide an upgraded and classified product. Gas velocity and temperature and the path and rate of movement of the ore through the gas are varied as required to obtain a given grade or size in the recovered colemanite product.

The apparatus used in practicing the method includes, in a preferred form, a tubular calcining drum which is inclined slightly with respect to the horizontal. Lifters are positioned along the internal wall of the calcining drum and the drum is rotated between two stationary end assemblies. Ore particles are introduced into the upper end of the drum and a stream of hot gas is introduced through the lower end of the drum. Rotation of the drum causes the ore to be repeatedly lifted and dropped across the gas stream while the ore simultaneously advances from the upper toward the lower end of the drum. The temperature of the advancing ore increases to the point required to cause decrepitation of the ore, and the gas stream flowing through the drum carries the particles of decrepitation to the upper end of the drum where they are removed and separated from the gas stream. In the preferred form, gas leaving the drum is conveyed to a second rotating, inclined drum which functions as a preheater for ore being introduced into the calcining drum.

1 Claim, 3 Drawing Figures 1 METHOD FOR PROCESSING COLEMANITE ORE This is a continuation, of application Ser. No. 183,846, filed Sept. 27, 1971, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention In its broader aspects, the present invention relates to methods for processing materials. The invention is used for processing colemanite ore which changes its physical characteristics upon heating to the extent required to permit the colemanite in the ore to be carried by a given fluid stream only after the colemanite ore under goes the change. The process is described herein with specific reference to colemanite ore materials which undergo a relatively sudden change in state in which large particles fragment into a large number of smaller particles when the large particles are heated to a critical temperature. As used herein, the term decrepitate" is employed to describe this relatively sudden fragmentation phenomenon. In the specific application to be described herein, the field of the invention relates to methods for calcining, upgrading and classifying colemanite ore materials of the type which decrepitate into relatively fine particles at a temperature below the temperature at which such materials fuse or agglomerate.

2. Brief Description of the Prior Art A common prior art method of processing ores such as colemanite and similar ores which decrepitate upon heating includes calcining the ore in a revolving, horizontally disposed kiln. Agglomeration or fusing of the decrepitated ore generally occurs and following the calcining process, the calcined ore must be crushed and passed through an air table or otherwise processed to separate the desired product from gangue or other impurity.

In another prior art process which eliminates the need for separate calcining and classifying steps, ore particles are calcined in a fluidized bed furnace in which an upwardly directed stream of gas is passed through the decrepitating ore to carry the finer particles of decrepitation away from the fluidized bed and the gangue. The gas and airborne particles are then separated to provide an upgraded, classified product.

Still another prior art process suggests the use of a vertical furnace having a stream of upwardly rising heated gases introduced at its lower end. Small ore par ticles are dropped into the top of the furnace and are increasingly heated as they fall downwardly toward the bottom of the furnace. Upon decrepitation of the particles, their change in state permits them to be carried upwardly out of the furnace by the rising gas stream where they may then be separated from the gas. Proper operation of the technique requires that the gas velocity be great enough to support or slow down the falling ore particles so that they may be heated to the point of decrepitation. Because of the relatively high gas velocity required to achieve this result, smaller particles of unprocessed ore are blown back and combined with the decrepitated ore particles. Where lower velocity gas flow is used in the latter technique, heavier particles of the ore fall completely through the furnace without reaching the temperature required for decrepitation. While it is theoretically possible to operate the lat ter process satisfactorily by introducing only ore parti- LII cles having a specific, uniform size and density, the time and expense required in sizing the raw ore would probably render the operation impractical.

SUMMARY OF THE INVENTION In the method of the present invention, a heated stream of relatively low velocity fluids is passed through an inclined, non-vertical treating area. As used herein, the term fluids" is intended to include gases.

t Colemanite ore particles are repeatedly elevated and dropped through the fluid stream and moved countercurrent to the stream. As the ore particles move countercurrent through the stream, they are increasingly heated until they decrepitate and undergo a relatively sudden shattering into many smaller pieces. The change in state caused by decrepitation permits the smaller particles of substantially pure colemanite to be moved by the fluid stream in the direction of fluid flow. Fluid and fluid carried particles leaving the treating area are separated by any suitable means. Gangue or other impurities in the ore which do not fragment or otherwise change state continue to move countercurrent through the treating area and are removed from the area after a predetermined exposure. By this process, an upgraded, classified material is continuously produced. It will be appreciated that the temperature of the fluid and the fluid velocity as well as the rate and path of movement of the ore through the fluid are varied to heat ore particles of a given size to the decrepitating temperature of the ore. Following decrepitation, subsequent heating which would cause agglomeration is prevented by the removal of the decrepitated material from the treating area by the flowing fluid. In the preferred form of the invention, the fluid stream is a stream of heated gas.

The preferred apparatus employed in the practice of the method of the present invention includes a treating area provided by a calcining drum which is mounted for rotation about a central axis which is inclined slightly with respect to the horizontal. A stream offlowing hot gas is introduced into the treating area at the lower end of the drum. Curved, blade-like lifting members extend inwardly from the internal wall of the drum. Upon rotation of the drum. the lifters elevate and then drop ore particles across the gas stream. The inclination of the drum causes the ore particles to advance toward the lower end of the drum as the particles are repeatedly elevated and dropped. The particles are increasingly heated at a controlled rate as they advance countercurrent to the gas flow until decrepitation occurs. The smaller particles produced by the decrepitation are carried by the flowing gases to the upper drum end where they are removed from the drum and separated from the gas. Those ore particles which do not undergo decrepitation continue to advance through the drum and are ejected at the lower drum end.

In the preferred form of the apparatus, a second rotating drum employs the hot gas separated from the decrepitated particles to preheat ore particles before the particles are introduced into the upper end of the first drum.

With the present invention, relatively low gas velocities may be employed to simultaneously upgrade and classify ore particles. Since the gas is not required to support or slow down a falling ore particle, the amount ofblow-back" of undecrepitated material is reduced. The relatively low velocity gas flow combined with the repeated dropping and gradual advancing of the ore particles through the gas stream provides a uniform heat gradient which permits close control over the heating of ore particles. Even where the input ore includes both relatively small and relatively large particles, blow-back and agglomeration are prevented because of the relatively low gas velocity employed and because of the close heating control provided by the repeated dropping of ore particles through the gas stream as the particles are advanced toward the lower, hotter end of the drum.

In the process of the present invention, ore is continuously upgraded and classified without the need for subsequent crushing, screening or air table operations. These and other features and advantages of the present invention may be more fully appreciated from the following specification, drawings and the related claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation, partially broken away schematically illustrating the preferred form of the apparatus employed in practicing the method of the present invention;

FIG. 2 is a cross-sectional view of a calciner of taken along the line 22 of FIG. 1; and

FIG. 3 is an enlarged, perspective view illustrating the lifters carried on the internal wall of the calciner.

DESCRIPTION OF THE PREFERRED METHOD In FIG. 1, the apparatus employed in practicing the method of the present invention is indicated generally at 10. The apparatus includes an input 11 which is designed to receive colemanite ore particles C and introduce the particles into a preheater 12 through an air lock 31. The ore passing through the preheater 12 is communicated through a connecting chute 14 equipped with a second air lock 15 into a treating area confined within a heating apparatus or calciner 16. Hot gas is introduced into the lower end of the calciner 16 through the combined operation of a suitable heater H and a blower B. The hot gas travels through the calciner 16 in the direction of the arrow 17 and leaves the upper end of the calciner throughan output line 18. The gas and any gas carried particles P in the gas are carried by the line 18 to a cyclone separator 19 which separates the particles P from the gas and deposits such particles on an output conveyor R. The particle free gas leaving the separator 19 is carried by a line 20 to the lower end of the preheater 12. Gas flowing through the preheater leaves the upper end of the preheater through an output line 21 where it is conveyed to a wet scrubber 22. The scrubbed gas leaving the scrubber 22 is pulled through an output duct 23 and into an exhaust fan F where it is then vented into the atmosphere.

The preheater 12 includes a tubular drum 12' mounted on rollers 12a and 12b. The drum 12' is rotated in the direction of the arrow 12c by an electric motor 12d acting through a small gear l2e which engages a larger gear 12f encircling the tubular drum. Upper and lower stationary end assemblies, 12g and 1211, respectively, engage the ends of the preheater drum 12' and function to provide a substantially leakproof seal with the rotating tubular body.

The heating apparatus or calciner 16 also includes a tubular body or drum 16a which is mounted on rollers 16b and 16c for rotation between stationary upper and lower end assemblies 16d and 16e, respectively. Suitable leakproof seals are provided between the end assembly 16a and 16e and the rotating body 1611. Rotation is imparted to the tubular body 16a by an electric motor and gear drive 16f acting through a small gear 163 which engages and imparts a rotary motion to a larger gear 16h encircling the body 16a. The lower end assembly 16e is provided with a tailings ejection chute 16k equipped with an air lock l6j.

The internal surfaces of the rotating drums employed in the calciner l6 and in the preheater 12 are similar and include curved lifters 24 connected to the internal drum walls in the manner illustrated in FIGS. 2 and 3. In the preferred form of the apparatus 10, the lifters 24 include a plurality of separate members which are separated from each other and extend axially in circumferentially spaced rows. Lifters in alternate rows are staggered with respect to each other and the free end of I each of the lifter members includes saw teeth 24a. As

best illustrated in FIG. 2, rotation of the drum causes the ifters to elevate ore particles from the bottom of the drum and release the particles when the lifters reach their upper position. The saw teeth 24a assist in spreading the ore particles as they fall to increase surface contact of the particles with the gas flowing through the drum.

In operation, small ore particles C are introduced into the inlet chute 11 by a conveyor belt asembly T or by other suitable means. The lower end of the chute 11 extends through the upper end assembly 12g and opens into the tubular body of the preheater l2. Ore falling through the chute 11 is passed through the air lock 13 before being admitted into the preheater to maintain desired pressures within the preheater. The air lock 13 is preferably operated by a suitable automatic control system (not illustrated) which causes the air lock to open and close as required to maintain suitable amounts of ore within the apparatus. The drum portion 12' of the preheater 12 rotates about an axis which is inclined slightly with respect to the horizontal. The inclination of the drum causes ore particles which are repeatedly .elevated and dropped by the lifters within the rotating drum body to advance through the drum toward the lower drum end. As the ore advances in this manner through the rotating drum, it is heated and dehydrated by the gas flowing through the drum.

The lifters adjacent the lower end of the preheater drum 12 drop the ore particles onto a tray 14a formed at the upper end of the connnecting chute 14. Ore dropping onto the tray 14a slides through the chute to the second air lock 15. The air lock 15 is operated automatically to open and close whereby the preheated ore is introduced into the treating area within the calcining drum 16a without permitting gases to flow through the chute 14. The lower end of chute 14 extents through the calciner end assembly 16d and drops the preheated ore into the upper end of the rotating drum 16a.

The central axis of the calcining drum 16a is also slightly inclined with respect to the horizontaland rotation of the drum causes the preheated ore particles at the upper end of the drum to be repeatedly elevated and dropped while they are advanced toward the lower end of the drum in a path substantially similar to that indicated by the arrow P. As the ore is moved th ough the drum, it is intimately contacted by the hot gas stream flowing in the direction of the arrow 17 and the temperature of the ore particles is gradually increased to the temperature required to cause decrepitation. The change in state of the particles associated with decrepitation permits the resulting smaller particles to be carried upwardly through the drum by the gas stream where they are removed from the treating area through the outlet duct 18 opening through the end assembly 16d. particles which are not carried in the direction of the gas flow advance through the drum and are ejected from the treating area through the air lock 16j in the tailings chute 16k.

The heated gas and particles carried by the gas trav eling through the duct 18 are introduced into a cyclone separator 19 which separates the heated gas from the decrepitated particles P. The particles P which are upgraded, classified colemanite taken from the raw, unprocessed colemanite ore are carried away by a con veyor R or other suitable means.

The hot gas separated by the separator 19 is communicated through the tube 20 into the preheater 12 where it functions to heat and dry the ore particles in the manner previously described. The gas leaving the preheater 12 through the output line 21 is cleaned of dust and other small particles by the wet scrubber 22. The exhaust fan F cooperates with the input blower B to provide the desired gas flow through the apparatus 10.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof, and various changes in the size, shape and materials as well as in the details of the illustrated construction may be made within the scope of the appended claims without departing from the spirit of the invention.

We claim:

1. A method of processing ore containing a combination of decrepitatable colemanite and nondecrepitatable gangue whereby the colemanite and gangue are separated from each other comprising the steps of:

a. flowing a heated gas stream linearly upwardly through a treating area along a path which is inclined with respect to the horizontal whereby the gas travels from a lower point to a higher point:

b. introducing said ore into said treating area at said higher point; t

c. repeatedly lifting and then dropping said ore while moving said ore through said gas countercurrent along a path substantially non-parallel to the direction of flow of said gas until the colemanite in the ore is gradually heated to a temperature equal to or above the point of decrepitation and below the point of fusing or agglomeration of the colemanite whereby the colemanite decrepitates and separates from the gangue;

d. moving the decrepitated colemanite with said gas stream in the direction of gas flow;

e. separating the gas-moved colemanite from the gas;

and

f. removing the gangue from the treating area at said 

1. A METHOD OF PROCESSING ORE CONTAINING A COMBINATION OF DECREPITATABLE COLEMANITE AND NONDECREPITATABLE GANGUE WHEREBY THE COLEMANITE AND GANGUE ARE SEPARATED FROM EACH OTHER COMPRISING THE STEPS OF: A. FLOWING A HEATED GAS STREAM LINEARLY UPWARDLY THROUGH A TREATING AREA ALONG A PATH WHICH IS INCLINED WITH RESPECT TO THE HORIZONTAL WHEREBY THE GAS TRAVELS FROM A LOWER POINT TO A HIGHER POINT; B. INTRODUCING SAID ORE INTO SAID TREATING AREA AT SAID HIGHER POINT; C. REPEATEDLY LIFTING AND THEN DROPPING SAID ORE WHILE MOVING SAID ORE THROUGH SAID GAS COUNTERCURRENT ALONG A PATH 